1. Scope of the Invention
The present invention relates to an apparatus permitting the treatment of bodily conduits, typically blood vessels, in an area of a bifurcation, e.g. in an area where a principal conduit separates into two secondary conduits. It also relates to equipment for positioning this apparatus.
2. Description of the Related Art
It is known to treat narrowing of a rectilinear blood vessel by means of a radially expandable tubular device, commonly referred to as a stent. This stent is introduced in the unexpanded state into the internal lumen of the vessel, in particular by the percutaneous route, as far as the area of narrowing. Once in place, the stent is expanded in such a way as to support the vessel wall and thus re-establish the appropriate cross section of the vessel.
Stent devices can be made of a non-elastic material, in which case the stent is expanded by an inflatable balloon on which it is engaged. Alternatively, the stent can be self-expanding, e.g. made of an elastic material. A self-expanding stent typically expands spontaneously when withdrawn from a sheath which holds it in a contracted state.
For example, U.S. Pat. Nos. 4,733,065 and 4,806,062 illustrate existing stent devices and corresponding positioning techniques.
A conventional stent is not entirely suitable for the treatment of a narrowing situated in the area of a bifurcation, since its engagement both in the principal conduit and in one of the secondary conduits can cause immediate or delayed occlusion of the other secondary conduit.
It is known to reinforce a vascular bifurcation by means of a stent comprising first and second elements, each formed by helical winding of a metal filament. The first of the two elements has a first part having a diameter corresponding to the diameter of the principal vessel, and a second part having a diameter corresponding to the diameter of a first one of the secondary vessels. The first element is intended to be engaged in the principal vessel and the second element is intended to be engaged in the first secondary vessel. The second element has a diameter corresponding to the diameter of the second secondary vessel. After the first element has been put into place, the second element is then coupled to the first element by engaging one or more of its turns in the turns of the first element.
This equipment permits reinforcement of the bifurcation but appears unsuitable for treating a vascular narrowing or an occlusive lesion, in view of its structure and of the low possibility of radial expansion of its two constituent elements.
Moreover, the shape of the first element does not correspond to the shape of a bifurcation, which has a widened transitional zone between the end of the principal vessel and the ends of the secondary vessels. Thus, this equipment does not make it possible to fully support this wall or to treat a dissection in the area of this wall. Additionally, the separate positioning of these two elements is quite difficult.